Cisco 1841 - cannot configure IP on Eth0/1 as it overlaps WIC ip

[georgewkenny]

Hi all. I have a Cisco 1841 which is connecting to an ISPs SDSL line provided with 8 ips.

When I try to configure the ETH0/1 interface with the second IP in the range, the Cisco SDM tells me that this is "overlapping" with the WAN0/1 interface ip (although they are different)

WAN is using 1st useable ip of the range
Eth is using 2nd useable ip of the range

any ideas?

 

[brianinms]

The SDM sometimes gives the wrong error messages. However you can't assign 2 ip addresses in the same subnet to the same interface. What are you trying to accomplish?

 

[georgewkenny]

Hi, thanks Braininms.

It may sound complicated, but I am trying to achive configuring the router in the same way its predecessor was configured.

WAN = 195.11.98.61/255.255.255.248
LAN1 = 195.11.98.62./255.255.255.248

Then LAN1 passes all traffic to firewall which is on 195.11.98.63.

If you think there is a more direct and convenient method, then please, I am all ears. All the Cisco needs to do is pass the WAN traffic direct to the FW to deal with. The FW is being reconfigured too, so we have a degree of flexibility.

 

[brianinms]

Oh okay, I now see the problem. Usually your WAN ip address is on a different subnet.

You could do

RouterA(config)# int fa0/1
RouterA(config-if)# ip unnumbered serial ?


Where ? is the serial interface id.